It is known to provide a suspension system for a vehicle such as a motor vehicle. One form of the suspension system includes a coil spring, one end of which rests in a lower seat moving with the wheel assembly; the opposite end contacts an upper seat of a vehicle body or frame of the vehicle. The spring supports the weight of the vehicle body and allows for reciprocating relative movement between the wheel assembly and the vehicle body during road travel to isolate wheel disturbances from the vehicle body.
In another form of the suspension system, a strut is mounted between the movable suspension elements and the body of the vehicle. The strut typically includes a hydraulic cylinder with an attached piston and piston rod. The piston rod slidably extends from an upper end of the hydraulic cylinder and is connected to the vehicle body through a flexible connection. The hydraulic cylinder is attached to movable suspension members at its lower end. The impact of shocks from the road surface causes movement of the piston, in turn, displacing fluid contained in the hydraulic cylinder. The resistance of movement of the piston through the hydraulic cylinder is dependent on the rate of displacement, thereby damping the movement of the associated spring and preventing excessive bouncing.
As the wheel assembly of the vehicle encounters road inputs, the suspension system undergoes compression (jounce) and extension (rebound) strokes. Current dampers in strut type suspension systems, exhibit effects that suggest a strong influence of stiction. The damper carries a radial load induced by reaction of static and dynamic forces in the suspension. This radial load binds the damper rod and tube at the rod guide and piston interfaces. The bind results in a relatively stiff suspension member because the damper rod ceases to freely move within the tube, defeating the advantageous effects of the displacement of the internal fluid. Under such conditions, the damper readily transmits unsprung suspension displacement, virtually lossless (as if it were elastic). Dynamic forces at the reaction interfaces of the vehicle body are much larger than desired, ultimately producing disproportionately large accelerations of the sprung mass.
As a result, it is desirable to provide a new damper assembly for a suspension system of a vehicle that is in series with an existing damper of a vehicle. It is also desirable to provide a damper assembly for a suspension system of a vehicle that provides damping and is stiction free. It is further desirable to provide a damper assembly for a suspension system of a vehicle that simultaneously reacts the relatively large static, quasi-static, and dynamic radial and bending loads without binding the damper. Therefore, there is a need in the art to provide a damper assembly for a suspension system of a vehicle that meets at least one of these desires.